Seems like there should be a way to embed some sort of coating or material in the windshield that would reject high-angle light. I understand the 3M Crystalline film has this feature, but it is not legal everywhere to apply film to the windshield even if it alllows >90% visible light through.

Imagine not only the heat reduction but also reduction of the reflected image of the dash in the windshield that creates a dangerous reduction in visibility on bright days. I wear polarized sunglasses in the car for that reason.